The dominance of non-electron-phonon charge carrier interaction in highly-compressed superhydrides

TL;DR

This study investigates the charge carrier interactions in superhydrides and finds evidence suggesting non-electron-phonon mechanisms, such as electron-magnon or electron-electron interactions, may be responsible for their high-temperature superconductivity.

Contribution

The paper challenges the prevailing assumption that electron-phonon interaction drives superconductivity in superhydrides by providing resistance measurements indicating alternative mechanisms.

Findings

Superhydrides exhibit power-law exponents p between 1.8 and 3.2.

High-entropy alloy shows p ≈ 4.9, consistent with electron-phonon interaction.

Results suggest non-electron-phonon interactions are likely responsible for superconductivity in superhydrides.

Abstract

The primary mechanism governing the emergence of near-room-temperature superconductivity in superhydrides is widely accepted to be the electron-phonon interaction. If so, the temperature dependent resistance, R(T), in these materials should obey the Bloch-Gr\"uneisen equation, where the power-law exponent, p, should be equal to the exact integer value of p=5. On the other hand, there is a well-established theoretical result that pure electron-magnon interaction should be manifested by p=3, and p=2 is the value for pure electron-electron interaction. Here we aimed to reveal the type of charge carrier interaction in the layered transition metal dichalcogenides PdTe2, high-entropy alloy (ScZrNb)0.65[RhPd]0.35, and highly-compressed elemental boron and superhydrides H3S, LaHx, PrH9 and BaH12 by fitting the temperature dependent resistance of these materials to the Bloch-Gr\"uneisen equation where the power-law exponent, p, is a free-fitting parameter. In the result, we showed that the high-entropy alloy (ScZrNb)0.65[RhPd]0.35 exhibited pure electron-phonon mediated superconductivity with p = 4.9. Unexpectedly we revealed that all studied superhydrides exhibit 1.8 < p < 3.2. This implies that it is unlikely that the electron-phonon interaction is the primary mechanism for the Cooper pairs formation in highly-compressed superhydrides and alternative pairing mechanisms, for instance, the electron-magnon, the electron-polaron, the electron-electron or other, should be considered as the origin for the emergence of near-room-temperature superconductivity in these compounds.